Bottom-supported casing



NOV. 28, 1967 c rrz ET AL BOTTOM-SUPPORTED CASING Filed Oct. 24, 1965INVENTORS ROBERT G CRITZ JAMES H C088 8 ATTOR NEYS United States Patent3,354,956 BOTTOM-SUPPORTED CASING Robert G. Critz and James H. Cobhs,Tulsa, Okla., assignors to Fenix & Scisson, Inc., Tulsa, Okla., acorporation of Oklahoma Filed Oct. 24, 1965, Ser. No. 504,345 4 Claims.(Cl. 16629) This invention relates to a bottom-supported casing.Particularly, the invention relates to a method of anchoring and sealinga large diameter casing in an earth bore hole. In another sense, theinvention relates to an anchored casing in an earth bore hole. Mostparticularly, the invention includes an anchored casing and a method ofanchoring a casing particularly adaptable for the anchoring of largediameter casing in an earth bore hole in a manner providing means ofcompensating for expansion and contraction of the casing as particularlyrequired when such casing is subjected to a high range of temperaturevariation.

In recent years the use of underground caverns for storing liquids hasgreatly expanded. One type of liquid which is frequently stored inunderground caverns is liquefied petroleum gas, including liquefiednatural gas. Liquefied gases must be maintained at very lowtemperatures. For instance, liquefied natural gas is stored attemperatures approaching minus 250 F. Thus, when liquefied natural gasis injected through a easing into an underground mine or cavern, thetemperature of the casing may change as much as 320 F.

Obviously, such large temperature changes will result in a substantialchange in the length of the casing, the change being proportional to thetotal length of the casmg.

One of the problems in the use of underground storage facilities isproviding a suitable anchor for the large diameter casing positioned inthe bore hole leading to the storage facilities. The usual means ofanchoring a casing is to support it in the bore hole and pour a hardsetting cement grout in the annulus exterior of the casing. This is theusual method in the petroleum industry and works completelysatisfactorily where relatively small diameter casing is used and Wherethe casing is not subjected to great temperature changes. However, thismethod has not proven satisfactory for large diameter casing subject tohigh ranges of temperatures changes. The expansion and contraction ofthe casing within hard setting grout ultimately pulls the casing loosefrom the grout permitting leakage which may permit water from strataabove the cavern to flow along the casing and into the cavern. Inaddition, if the expansion does not pull the casing loose from thegrout, the casing may be confined and can be subjected to buckling andso forth.

It is therefore an object of this invention to provide an improvedmethod of anchoring and sealing a casing supported in an earth borehole.

Another object of this invention is to provide an anchored casingarrangement for an earth bore hole which is particularly useful foranchoring large diameter casing subject to a wide range of temperaturevariation.

These and other objects of the invention will be explained and anunderstanding of the invention will be had by referring to the followingdescription and claims taken in conjunction with the attached drawingsin which:

FIGURE 1 is a crosssectional view of a casing anchored in the earthcommunicating with an underground cavern according to the principle ofthis invention.

FIGURE 2 is a cross sectional view of the anchored casing taken alongthe line 2-2 of FIGURE 1.

Referring to FIGURE 1, a casing is shown supported in an earth bore hole12 which communicates with an underground cavern 13. The bore hole 12 isalways larger in diameter than the external diameter of the casing 10,leaving an annulus 14. As previously indicated, the normal means ofanchoring the casing is to fill the annulus 14, usually from the bottomof the casing to the surface of the earth, with a hard setting cementgrout. While this method works completely satisfactorily for smalldiameter casing and particularly installations where relatively smallranges of temperature variations are encountered, such an arrangementhas not proven satisfactory for large diameter casing subject to hightemperature variations.

By the method of this invention, before inserting the easing into thebore hole 12, the upper portion thereof is covered with a lubricatingcompound layer 16. Such lubricating compound layer 16 may be of anymaterial which will prevent a hard setting grout from adhering to casing10 and includes the use of heavy grease or some similar material.

The lower portion of casing 10, such lower portion being designated bythe numeral 18, is uncoated and may be especially prepared, ifnecessary, by cleaning or otherwise, so that hard setting cement groutwill adhere to it. With the casing 10 in position in the bore hole, ananchoring strata of hard setting grout 20 is poured into the annulus 14which serves to anchor the bottom of casing 10 to the walls of the borehole 12. Next, a strata of chemical seal 22 is poured in the annulus 14.The chemical seal strata 22 rests upon the top of the anchoring strata20. It contacts casing 10 and fills all of the exterior of the loweruncoated portion 18 above the anchoring strata 20.

Next, a stabilizing hard-setting grout 24 is poured to fill the annulus14 between the luburicating coating 16 and the interior wall of the borehole 12.

A plurality of anchoring bolts 26 are installed through the lowerportion of casing 10 and into the wall of the earth bore hole 12. Theanchoring bolts 26 extend through the anchoring strata 20.

Anchoring bolts 26 and the anchoring strata 20 combine to anchor thebottom of casing 10 to the earth with the casing 10 extending upwardlyto the surface of the earth. The chemical seal 20 prevents leakage ofsubsurface water from flowing along the casing 10 and into theunderground cavern 13.

The casing 10, being anchored only at the bottom, is free to contractand expand along its entire length to the surface. When the casing 10 issubjected to temperature change, the lubricative layer 16 permits freeexpansion and contraction in length so that no stress or strain isplaced upon the casing or the stabilizing grout 24.

The anchoring grout 20 and the stabilizing grout 24 are of a hardsetting material, such as cement.

The chemical seal strata 22 is composed of any material which remainsfluid or at least plastic at the lowest temperature to which casing 10will be subjected. In the instance wherein casing 10 is utilized toconvey liquefied natural gas into an underground cavern 13, the chemicalseal 22 must remain plastic to at least minus 260 F., the minimumexpected temperature. When the casing 10 will be subjected to a smallerrange of temperature variation wherein the lowest expected temperatureis higher than that for liquefied natural gas, the liquid chemical seal22 may be of greater variety of compounds. Thus, the selection of thematerial of which the chemical seal 22 is composed will be dependentupon the minimum temperature to which the casing 10 will be subjected.

This invention provides a greatly improved means of anchoring largediameter casing in a manner such that a continuous waterproof seal canbe provided in a manner permitting the expansion and contraction of thecasing without causing damage to the casing or to the stabilizing groutwhich supports the casing in the earth bore hole and without destroyingthe seal of the casing to the bore hole.

While this invention has been described with a certain degree ofparticularity, many changes may be made in the details of constructionand the arrangement of components wthout departing from the spirit andscope of this disclosure.

What is claimed:

1. A method of anchoring and sealing a large diameter casing in an earthbore hole comprising applying to the exterior of the upper portion ofsaid casing a lubricative compound,

lowering the casing in the bore hole with the uncoated portion at thebottom,

pouring an anchoring strata of grout in the annulus between the lowerportion of the uncoated portion of the casing and the bore hole,

pouring a strata of chemical seal in the annulus between the upperportion of the uncoated portion of the casing and the bore hole, thelower surface of the chemical seal strata resting upon the upper surfaceof the anchoring grout strata, and

pouring a grout in the annulus between the coated portion of the casingand the bore hole.

2. A method of anchoring and sealing large diameter casing according toclaim 1 including the step of installing rocn bolts between the casingand the earth bore hole wall through the anchoring grout.

3. An anchored casing in an earth bore hole comprising a length ofcasing positioned in said bore hole,

an anchoring strata of hardsetting grout in the annulus 4 between thelower portion of the casing and the bore hole,

a strata of chemical sealing compound between the easing and theannulus, the chemical seal strata bottomed on the anchoring groutstrata,

a layer of lubricating compound on the exterior of that portion of saidcasing above said chemical seal strata, and

stabilizing hard setting grout in the annulus between said layer oflubricating compound and the bore hole wall above said strata ofchemical sealing compound.

4. An anchored casing according to claim 3 including a plurality of rockbolts extending through the wall of said casing and into the wall ofsaid bore hole, said rock bolts extending through said anchoring groutstrata.

References Cited UNITED STATES PATENTS 2,080,406 5/1937 Allen 61-41 X2,787,125 4/1957 Benz 61-.5 3,055,424 9/1962 Allen 16621 3,216,20011/1965 Scisson et a1 166-21 X 3,221,505 12/1965 Goodwin et al. 166-29 X3,307,361 3/1967 Waterman 61-4l CHARLES E. OCONNELL, Primary Examiner.

DAVID H. BROWN, Assistant Examiner.

1. A METHOD OF ANCHORING AND SEALING A LARGE DIAMETER CASING IN AN EARTHBORE HOLE COMPRISING APPLYING TO THE EXTERIOR OF THE UPPER PORTION OFSAID CASING A LUBRICATIVE COMPOUND, LOWERING THE CASING IN THE BORE HOLEWITH THE UNCOATED PORTION AT THE BOTTOM, POURING AN ANCHORING STRATA OFGROUT IN THE ANNULUS BETWEEN THE LOWER PORTION OF THE UNCOATED PORTIONOF THE CASING AND THE BORE HOLE, POURING A STRATA OF CHEMICAL SEAL INTHE ANNULUS BETWEEN THE UPPER PORTION OF THE UNCOATED PORTION OF THECASING AND THE BORE HOLE, THE LOWER SURFACE OF THE CHEMICAL SEAL STRATARESTING UPON THE UPPER SURFACE OF THE ANCHORING GROUT STRATA, ANDPOURING A GROUT IN THE ANNULUS BETWEEN THE COATED PORTION OF THE CASINGAND THE BORE HOLE.